package org.apache.lucene.store;

/**
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

import org.apache.lucene.util.BytesRef;

/** @lucene.experimental */
public final class ByteArrayDataInput extends DataInput {

    private byte[] bytes;

    private int pos;
    private int limit;

    public ByteArrayDataInput(byte[] bytes) {
        reset(bytes);
    }

    public ByteArrayDataInput(byte[] bytes, int offset, int len) {
        reset(bytes, offset, len);
    }

    public ByteArrayDataInput() {
        reset(BytesRef.EMPTY_BYTES);
    }

    public void reset(byte[] bytes) {
        reset(bytes, 0, bytes.length);
    }

    public int getPosition() {
        return pos;
    }

    public void reset(byte[] bytes, int offset, int len) {
        this.bytes = bytes;
        pos = offset;
        limit = offset + len;
    }

    public boolean eof() {
        return pos == limit;
    }

    public void skipBytes(int count) {
        pos += count;
        assert pos <= limit;
    }

    @Override
    public short readShort() {
        return (short) (((bytes[pos++] & 0xFF) << 8) | (bytes[pos++] & 0xFF));
    }

    @Override
    public int readInt() {
        assert pos + 4 <= limit;
        return ((bytes[pos++] & 0xFF) << 24) | ((bytes[pos++] & 0xFF) << 16) | ((bytes[pos++] & 0xFF) << 8) | (bytes[pos++] & 0xFF);
    }

    @Override
    public long readLong() {
        assert pos + 8 <= limit;
        final int i1 = ((bytes[pos++] & 0xff) << 24) | ((bytes[pos++] & 0xff) << 16) | ((bytes[pos++] & 0xff) << 8) | (bytes[pos++] & 0xff);
        final int i2 = ((bytes[pos++] & 0xff) << 24) | ((bytes[pos++] & 0xff) << 16) | ((bytes[pos++] & 0xff) << 8) | (bytes[pos++] & 0xff);
        return (((long) i1) << 32) | (i2 & 0xFFFFFFFFL);
    }

    @Override
    public int readVInt() {
        checkBounds();
        byte b = bytes[pos++];
        int i = b & 0x7F;
        for (int shift = 7; (b & 0x80) != 0; shift += 7) {
            checkBounds();
            b = bytes[pos++];
            i |= (b & 0x7F) << shift;
        }
        return i;
    }

    @Override
    public long readVLong() {
        checkBounds();
        byte b = bytes[pos++];
        long i = b & 0x7F;
        for (int shift = 7; (b & 0x80) != 0; shift += 7) {
            checkBounds();
            b = bytes[pos++];
            i |= (b & 0x7FL) << shift;
        }
        return i;
    }

    // NOTE: AIOOBE not EOF if you read too much
    @Override
    public byte readByte() {
        checkBounds();
        return bytes[pos++];
    }

    // NOTE: AIOOBE not EOF if you read too much
    @Override
    public void readBytes(byte[] b, int offset, int len) {
        assert pos + len <= limit;
        System.arraycopy(bytes, pos, b, offset, len);
        pos += len;
    }

    private boolean checkBounds() {
        assert pos < limit;
        return true;
    }
}
